A laparoscopic operation, such as a laparoscopic cholecystectomy, forms a small incision in the patient's abdominal wall, inserts a trocar tube in the small incision, inserts an endoscope and a pair of forceps through the trocar tube into the peritoneal cavity, and the operator conducts a surgical operation, visually watching an image taken by the endoscope and displayed on the screen of a monitor. Since the laparoscopic operation does not involve laparatomy, a burden on the patient is small, the patient recovers quickly after the operation, and the number of days for which the patient needs to stay at the hospital after the operation is reduced greatly. Thus, the laparoscopic operation is excellent in not exerting a large burden on the patient and the field of application of the laparoscopic operation is expected to expand. On the other hand, the laparoscopic operation does not permit the direct visual observation of the affected part, and requires techniques of skilled operators because only a difficult-to-operate pair of forceps provided with only a gripper capable of opening and closing is available.
Studies have been made to apply a medical master/slave manipulator including a control unit (master unit) having a plurality of degrees of freedom of motion, and a working unit (slave unit) having a plurality of degrees of freedom of motion and capable of reproducing the motions of the control unit to laparoscopic operations, and medical master/slave manipulators have been practically applied to laparoscopic operations. A remote-control master/slave manipulator of a complicated system includes a maser unit and a slave unit which are spaced a long distance apart. If the slave unit remote from the master unit should become out of control, the patient is exposed to a fatal danger. Therefore, it is possible that safety problems arise when the remote-control master/slave manipulator is applied to medical uses.
A simple, easy-to-operate connected medical master/slave manipulator has a common shaft common to a master unit and a slave unit. A known connected master/slave manipulator for the field of industrial robots has a master unit and a slave unit. In all those known manipulators, the orientation of the master unit is adjusted to that of the slave unit instead of adjusting the orientation of the slave unit to that of the master unit in a transient master/slave operation mode in which an unrestricted operation mode changes into a master/slave operation mode to reduce the orientation difference between the master unit and the slave unit to zero, because the adjustment of the master unit lying near the operator is easy and, in the operation of an industrial robot provided with a master unit and a large, heavy slave unit, the operation of the large, heavy slave unit for the adjustment of its orientation to that of the master unit is not practically feasible.
When operating a medical master/slave manipulator, the slave unit cannot be controlled as an operator likes and the medical master/slave manipulator is difficult to operate if the operation of the medical master/slave manipulator is started before the master unit and the slave unit are aligned. There have been proposed methods of aligning the master unit and the slave unit of master/slave manipulators. In a master/slave manipulator including a slave unit, a master unit, shape-recognizing means incorporated into the slave and the master unit, and a comparing means for comparing the results of recognition made by the shape-recognizing means, these methods require the operator to adjust the shape of the master unit to that of the slave unit, and then start the master/slave manipulator for a master/slave operation. Thus, in a transient master/slave operation mode in which an unrestricted operation mode changes into a master/slave operation mode, the master unit is so controlled as to adjust its orientation to that of the slave unit.
Thus, those known methods require the operator to perform a shape-adjusting operation for adjusting the shape of the master unit to that of the slave unit every time the master/slave operation is started or resumed. The operability of such a master/slave manipulator is not necessarily satisfactory. Since the adjusting operation must be performed for a plurality of degrees of freedom of motion, the shape-adjusting operation takes much time. In a medical manipulator capable of moving with degrees of freedom of motion and having a master unit that does not necessarily needs any degree of freedom of motion, such as a gripper, it is difficult to achieve shape-adjustment through the operation of only the master unit. These problems will make it difficult to take such steps as the occasion demands when an unexpected accident occurs during a practical operation.